Two projects will be conducted utilizing existing data sets from Missouri Alcohol Research Center (MARC) studies. The first data set is from a cohort-sequential study of twins from early adolescence through young adulthood. These data, taken from the Missouri Adolescent Female Twin Study in conjunction with the MARC, will be used to apply three different models used for working with longitudinal, genetically informative data in order to examine change in drinking patterns over a period of active development in drinking behavior. The models applied will be designed to uncover stable individual factors or trajectories over the course of the study duration, and to partition these variabilities into genetic and environmental components. The second data set is from a study of dynamic posturography in individuals with a family history of alcoholism. These data set will be used to illustrate the use of dynamic factor analysis, a very appropriate but underutilized tool for modeling the effects of time. The hypotheses that smoking attenuates the lagged sensory-motor responses that individuals produce in response to alcohol will be investigated. In addition, to make these analytical tools more accessible to the alcohol research community, a Visual Basic" computer program will be developed to specify and compare these models.